This invention relates to air bag sensor modules that are secured to the vehicle structure for transmission of crash pulses, and more specifically, the invention relates to a fastening device for securing the module to the vehicle structure.
Air bag sensor modules include a crash sensor and are mounted on the vehicle structure in a manner to transmit crash information from the vehicle structure to the crash sensor. Diagnostic circuits evaluate the crash information and discriminate between a fire and a no fire condition. To this end, the air bag sensor module is mounted on the vehicle such that the crash sensor will be subject to forces that indicate a crash condition. For example, the crash sensor usually comprises an accelerometer and the air bag module is rigidly coupled to a portion of the vehicle such that deceleration indicative of a crash condition is transmitted to the crash sensor. When a crash condition requiring air bag deployment is detected, the controller associated with the air bag module sends a signal to ignite an air bag deployment device.
To ensure that the forces are properly transmitted from the vehicle structure to the crash sensor, the module must be securely fastened to the vehicle structure. Typically, the manufacturer of the module supplies the module to the vehicle manufacture, which provides the fastening elements used to secure the module to the vehicle structure and installs the module onto the vehicle structure. Preferably, the fastening elements are secured to the vehicle structure only under the compressive load of a threaded fastener to ensure optimal crash pulse transmission. By having the vehicle manufacturer supply the necessary fastening elements, variables are introduced that may compromise proper installation of the module and inhibit crash pulse transmission. For example, the threads of the fastener may engage both the module and the vehicle structure so that the module is not secured to the vehicle structure by compressive load alone. Additionally, the shaft of the fastener may be in an interference fit relationship with a module mounting hole, again preventing the module from being secured to the vehicle structure by compressive load alone. Therefore what is needed is a fastening device which secures the module to the vehicle structure only by the compressive load of the fasteners to ensure optimal crash pulse transmission.